Unknown Virus

Hi
My computer has a boot virus that is not detected by any virus scanner. My bios virus protection detects a boot virus but can fix it or identify it.
It puts different coloured blocks of colour all through parts of the screen during load up, and will randomly shut down, and freeze.
It also stuffs up directx games and programs in windows. My other partion of linux gets no effects.
I believe this virus travels by disk, because the disk drive lights come on at unusal times.
I cant find any unusual files on my harddisk or any odd things in the sis ini and wiin ini files so i cant send nod a sample of the virus.
I also I believe i have had this virus for alot longer than it has been doing very noticable things and that it survived a format by placing itself in my graphics card memory,(winfast A380 geforce 4 ti4200 chipset) i tried doing a graphics bios flash and reseting the memory of the card but no such luck, and this virus is really restricting my computer in alot of ways. It sometimes takes up to 20 reboots before i can get it into windows successfully.
I would appreciate any help.
Thank you.

In addition to the other points/suggestions made above, I think you should consider the possibility that the BIOS virus protection on the systemboard is preventing your scanner from detecting/diagnosing/cleaning the virus. I have always felt that these Motherboard BIOS Virus protection arrangements were far more trouble than they are worth. I would recommend that you go into the BIOS setup and disable the Virus Protection (don't change anything else!) and save your change and when you boot into Windows give your scanner another chance to deal with it.

If you are unsure how to get into the BIOS setup, gracefully shut down your system so it is completely powered off and then when you turn on the power look for some text indicating the keys to press to enter the BIOS (It might be one of the following; F1 or F2 or F10 or a sequence like Alt+A or just about anything else, you need to press that sequence repeatedly before the monitor shows the windows GUI starting to come up